Testing device



A.v M. RENNAU TESTING DEVICE Dec. 21, 1937.

Filed Aug. 6, 1935 A Zart Ra /maze BY myzw l l HIS ATTORNEYS Patented Dec. 21, 1937 PATENT OFFICE I TESTING DEVICE Albert M. Rennau, Hannibal, Mo., assignor oi.

forty percent to Robert H. McKinney, Hannibal, Mo.

Application August 6, 1935, Serial 34,964

5 Claims.

My invention relates to electric motors and generators, and has among its objects and advantages the provision of an improved testing device.

In the accompanying drawing:

Fig. 1 is a ,top plan view of the device;

Fig. 2 is a side elevation;

Fig. 3 is an enlarged sectional view along the line 3-3 of Fm. 2;

Fig. 4 is a view taken along the line 4-4 of Fig. 3;

Fig. 5 is a sectional view illustrating my extension feature; and

Fig. 6 is a perspective view illustrating the use of the device for testing purposes.

In the embodiment selected to illustrate my invention, I make use of a coil head Ill connected with an ampere-meter box l2 through the medium of a tubular member l4. Within the box I2 I mount an alternating current repulsion vane or direct current rectifier type ampere-meter I 6. The ammeter I6 is electrically connected with a coil l8 in the head l through the medium of conductors housed within the tubular member l4.

In Fig. 3 the head l0 comprises a cap 20 having interfitting relation at 22 with the part 24. An opening 26 is provided in the cap 20 for the reception of the neck 28 of an iron pole piece or core 30. I rivet the neck 28 at 32 to fixedly connect the pole piece with the cap. The riveted end 32 embodies a curvature conforming to the cap 20 whereby the riveted end may'be placed in contact with the laminations of the machine being tested.

Upon the pole piece I mount a fiber washer 34 adjacent the cap 20 and reduce the inner end of the pole piece at 36 for the reception of a fiber washer .38. Between the two washers and upon the pole piece 30 I wind a coil 40 of magnet wire, which coil is electrically connected with the two conductors 42 and 44 within the tubular member I4. I prefer toprovide the pole piece 30 with a threaded bore 46 for the reception of a bolt 48 extending through an opening 50 in the part 24. Thus the cap 20 may be drawn firmly into connected relation with the part 24 by tightening the bolt 48.

One end of the tubular member I4 is pressed onto a neck 52 cast integrally with the part 24. The coil head ill, the member l4, and the ammeter box l2 are preferably made of aluminum or other suitable material having non-magnetic properties.

Within the upper end of the member I4 I mount a tubular insert 54 having a closed end 58 source, which in most cases would be the same provided with openings for the reception of spring contacts 58 and BI] connected with the conductors 42 and 44, respectively. The insert 54 is formed of insulating material. Grooves 62 and 64 are formed in the inner wall of the insert 54 for the reception of the contacts 58 and 6B.

To the hollow neck 66 formed integrally with the ammeter box I2, I connect a plug 68 arranged to be inserted in the insert 54. The plug 68 comprises a brass sleeve contained within an in- 10 sulating sleeve 12 pressed into the neck 66. With the brass sleeve 10 I mount an insulating member 14 having alongitudinal bore for the. reception of a conducting wire 16. I provide the member 14 with a shoulder 18 arranged to abut the ammeter l6 at 84. A second wire 86 electrically connected with the ammeter l6 at 88 is electrically connected with the brass sleeve H1 at .90. Because of the plug 68 the ammeter box l2 may be disconnected from the tubular member l4. With the parts arranged according to, Fig. 3, the metallic tip 80 is positioned in electrical contact with the contact 58, while the brass sleeve 10 is in electrical contact with the contact 60.

I illustrate the ammeter l8 as being'provided with a flange 92 lying over the end 94 of the ammeter box. The end 94 may be provided with a plurality of threaded openings 96 for the reception of screws 98 passing through openings in the flange 92 for detachably securing the ammeter to the box. In operation (see Fig. 6), my device is employed for testing electric motor and generator windings by disassembling the device being tested.

This feature eliminates all danger of damaging the machine being tested. For testing purposes the end 32 of the pole piece 30 is placed at the approximate center of the pole to be tested. Be-

fore the test is taken, the wires I00 and I02 of the winding being tested are electrically connected with conductors I04 and H16, respectively. I provide a variable resistance I08 having electrical connection with the separated ends of the conductor I04, and the latter and the conductor I06 are connected with a conventional plug I ill for connection with a conventional outlet for an alternating current supply.

With my invention the machine being tested receives its current from an alternating current current under which the machine operates in service. The variable resistance I08 is set for a suitable reading on the ammeter I8. All poles are tested in the same manner without changing the resistance I08. Thus by comparison of readings, shorted or reversed polarity turns can be easily recognized by variations in the ammeter reading.

In many cases it may be desirable to provide an extension for the tubular member It for increasing the distance between. the ammeter and the coil head I0. My extension provides an accurate reading of the ammeter under all conditions of service. The accuracy or the instrument may be impaired when held in close proximity with powerful magnetic fields. The extension provides accommodation for variable conditions of operation, to the end that the instrument may be positioned at a suflicient distance from the mechanism being tested.

In Fig. 5 I provide a cap II2 of insulating material having a bore Ill for thereception oi the plug 68. The cap II2 includes two spring contacts H6 and N8 of the same construction as the contacts 58 and 60. The wall of the bore I4 has frictional contact with the plug to hold the two parts in connected relation. I thread the neck I20 of the cap M2 for the reception of a protector I22 mounted thereon. This protector enclwes the connections between the wires I24 and I25 and the contacts H6 and I88. The wires I25 and I26 are grouped as a cord I28, and the opposite ends of the wires I24 and I26 are electrically connected witha plug I30 oi the same construction as the plug 68. I anchor the plug I30 in an insulating body I32 having threaded relation at I34 with a protective cap I38 of insulating material.

In making tests with the extension, the parts are arranged according to Fig. 5, and the plug I30 inserted in the insert 54 iorestablishing electrical contact between the plug I30 and the contacts 58 and 60. Otherwise the procedure for testing purposes is the same. The cord I28 may be of any, desirable length.

I provide a testing device which is light in weight, whereby an ideal portable device is provided. The tester requires no outside field of excitation other than that of the motor being tested. My device is used for testing purposes, while the machine is not in operation, thereby eliminating the danger of damaging the machine. In addition the device may be used for testing reverse polarity of turns within a pole.

My device may be used for testing both the rotor and stator of a machine. The machine being tested receives its current from an alternating current source so that tests are made under current conditions commensurate with that under which the machine operates in service. A short will be more likely to appear with the machine tested under normal voltage.

Without further elaboration, the foregoing will 'so fully explain my invention that others may,

by applying current knowledge, readily adapt the same for use under various conditions of service. 1

I claim:

1. A'device oi the type described comprising a hollow head, a pole piece mounted within the head and havinga part extending to the exterior thereof and being adaptable to be positioned in arcane operating proximity with a machine partbeing tested, a coil wound upon said pole piece, an ammeter, a tubular member connecting the ammeter with'said head, and electrical connections between the ammeter and said coil and being housed within the tubular member, said tubular member and said electrical connections being separable, and an extension for operatively connecting the separated tubular member including electrical connections connectible with said separated electrical connections.

2. A device or the type described comprising a hollow head, a pole piece mounted within the head and being arranged to be positioned in operating proximity with a device being tested, a coil carried by said pole piece, a tubular member connected with the head, an ammeter, a box for containing the ammeter and having a tubular extension, a plug positioned inside the tubular extension and being electrically connected with said ammeter, and electrical conductors mounted in said tubular member and operatively connected with said coil, said plug being insertable within the tubular member and having electrical contact with the conductors in the latter.

3. A device of the type. described comprising a hollow head, a pole piece mounted within the head and being arranged to be positioned in operating proximity with a device being tested, a coil carried by said pole piece, a tubular member connected with the head, an ammeter, a box for containing the ammeter and having'a tubular extension, a plug positioned inside the tubular extension and being electrically connected with said ammeter, electrical conductors mounted in said tubular member and operatively connected with said coil, said plug being insertable within the tubular member and having electrical contact with the conductors in the latter, said plug being removably retained within the tubular member, an extension comprising an insert plug shaped to be inserted in the tubular member,

electrical conductors connected with said lastnamed plug, and a socket connected with said last-named electrical conductors, said socket being adapted to receive saidflrst-named plug for establishing electrical connection between the latter and the last-named conductors.

'4. In a testing device of the type described, a hollow head comprising two sections, a pole piece connected with one section, a screw connected with the other section and having threaded relation with the pole piece for connecting the two sections, said pole piece having a portion extending to the exterior of the head, to be positioned in operatingproximity with a part to be tested, a coil mounted on said pole piece, an elec-- trical measuring instrument, a support therefor, and an operating electrical connection between the coil and the electrical measuring instrument. 5. In a testing device oi? the type described, a head comprising two sections, a pole piece carried by one of said sections and having a portion positioned to be placed in operating proximity with a part being tested, connecting means between the other section and the pole piece for holding the two sections in connected relation, a coil carried by said pole piece, an electrical measuring instrument carried by said head, and an operating electrical connection between the coil and the electrical measuring instrument.

ALBERT M. RENNAU. 

